Chalcedony – Properties, origins & identification

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Chalcedony

Pale blue to blue-grey, waxy translucent

Blue Grey White

Optical properties

Optical characteristics

Ref. index: 1.53 – 1.543
Birefringence: 0.004
Luster: Waxy
Pleochroism: None None.
Fluorescence: Some pale blue chalcedony fluoresces weak white-blue under SW UV.

Origins

Important source for color-change diaspore; also a major chalcedony producer.

Major source for beryl, tourmaline, quartz, topaz, chrysoberyl and rare minerals.

Known for demantoid, spessartite and collector minerals; also produces fine blue chalcedony.

Historic and modern source for garnet, moonstone, corundum and other gems.

Diverse sources for turquoise, tourmaline, opal, sapphire, topaz, red beryl and rare minerals.

Treatments

Inclusions

Identification

10x Loupe Your most-used instrument, start every examination here Refractometer Measures refractive index, the backbone of gem identification Hydrostatic Scale Measures specific gravity, works even on opaque stones UV Lamp, Long Wave and Short Wave Fluorescence exposes treatments, synthetics, and origin

Specifications

Market price $ 2 – 60 / ct

Rarity Very Common

Chalcedony is very common; fine blue chalcedony from Namibia and Turkey is the most prized form.

Confused with

Turquoise Turquoise has lower hardness, matrix veins, and different RI.
Opal Opal has lower SG, higher water content, and often a distinctive play-of-color.

Expert tip

Blue chalcedony from Namibia and Turkey is most prized for its uniform soft blue; always check for dye concentration along cracks.